Peristomium about as long as head, a little wider on posterior than on anterior margin, and only faintly marked off from the second somite, which is about half as long as it. Succeeding somites practically uniform in width and length until they narrow at posterior end. Anal cirri inconspicuous, but one of the two pairs much longer than the other.
The gills begin in the type specimen on the right side on somite 25 with a double filament; on the left they begin with one filament on 24, becoming double on 25. In later somites the filaments increase rapidly in length and new ones appear irregularly, the largest number I could find on the type being 5. Toward the posterior end the number again diminishes, and the last gill was on the twenty-fourth somite from the pygidium. The branches of all gills are long and straight, but except in contracted individuals they do not meet across the dorsal surface of the body (plate 2, fig. 14).
First parapodium with dorsal and ventral cirri about equal in length and with a conical post-setal lobe. The setal lobe bears several aciculie (plate 2, fig. 15). The tenth parapodium with a rounded dorso-lateral post-setal lobe, the setal portion with two lobes, one dorso-posterior, the other ventro-anterior. The dorsal cirrus has a constricted base, then broadens, and finally narrows to a rounded tip. The ventral cirrus has a broad base of attachment and is bluntly rounded at apex.
A parapodium from the middle of the body has rounded setal lobe, whose anterior and posterior lips are about equal in size (plate 2, fig. 14). The dorsal cirrus is small and does not extend much beyond the setal lobe. The ventral cirrus has a broad base, and a small cylindrical terminal portion. The gill filaments are about equal in length and arise from a broad base. There are two dorsal aciculle having rounded ends, while a ventral acicula with bifid end emerges just dorsal to the ventral cirrus. Behind the gill-bearing somites the cirri become more prominent, the dorsal being the more slender of the two.
Simple setae slender with swollen pointed apex having entire edges. Com pound seta (plate 2, fig. 16) has prominent serrations on the end of the basal joint, the terminal joint long, gently curved, without teeth. Pectinate seta of two kinds; in the anterior somites they have about 20 very minute teeth, the end ones being a trifle longer than the others (plate 2, fig. 17). Posteriorly
are found asymmetrical pectinate seta (plate 2, fig. 18) flattened more than the others and with only about 8 prominent teeth. In the middle somites both kinds may occur. The dorsal acicula; are rounded at the end, and are darker in anterior than in posterior somites. The ventral a,cicuhe are lighter in color than these, and are bifid at the end. In the posterior somites there occur, what I could not find in the anterior, needle aciculEe extending into the dorsal cirrus.
Jaws very dark, the forceps large with respect to the base, curved through 20°. The proximal paired plates have 5 teeth on the left side and 6 on the right. Distal paired plates with 7 on the right and 4 on the left. The unpaired plate with 8 (plate 3, fig. 1) teeth. The mandibles had very long, slender, dark shafts, the beveled portion being small and its surface white, except for a black outer edge (plate 3, fig. 2).
Collected July 1915 at Mangrove Key, Key West Harbor; Boca Grande; and at Marquesas, in sandy mud within digging distance of low-water mark. Type in American Museum of Natural History.
Marphysa nobilis n. sp.
A large species, one specimen of average size measuring, after preservation, 350 mm. in length, with a peristomial diameter of 4 mm. The three somites following the prostomium were of the same breadth as the prostomium, but there was a later gradual enlargement to 7 nun. at the seventeenth somite. Behind this there was a gradual narrowing to the posterior end, this narrowing being more evident from somite 17 to somite 30. These measurements were taken on preserved material in which the relative proportions may not have been exactly as in life.
The body of the living animal is a flesh color due to the contained blood, and anteriorly is markedly iridescent. The only pigmentation of the surface is in the form of green bands on the otherwise colorless tentacles and numerous yellowish spots scattered over the anterior surface of the body. The posterior part of the body during life is decidedly transparent. Preserved material is uniformly brownish gray. In life, the red gills give a decided tint to the middle portion of the body.